The question of whether or not Jessica Biel had a nose job has never been "officially" settled. There's no great before and after photos on her plastic surgery, but the shape of her current nose just looks unnatural. Not many people have as thin and "sculpted" of a nose as she has without going under the knife. The bridge of her nose looks too thin in relation to the top of her nose. See how the width is noticeably wider at the top?
If Jessica Biel had a nose job, the bridge and tip were narrowed. The surgeon would likely have shaved the bone in the bridge, and resculpted the tip.
Jessica Biel's nose actually looks a little bit bigger this before photo. But the difference could just be attributed to the lighting and not plastic surgery.
Her nose looks jagged and uneven in the left picture. It definitely looks more appealing in bright lights (as does anyone's nose though).
If Jessica Biel had the plastic surgery, it would have been at a very young age.